This disclosure relates to fenestration systems. Fenestration systems can include door and window openings such as glazed inswing doors, glazed inswing windows, glazed outswing doors, glazed outswing windows, glazed bifold doors, glazed pivot doors, and fixed-lite fenestrations. Specifically, this disclosure relates to “high-performance” (i.e. weather performing and energy efficient) fenestration systems.
High-performance fenestration systems are designed to protect building interiors from wind and rain and improve energy efficiency. A typical high-performance fenestration system includes a frame surrounding the fenestration opening and a movable glass panel surrounded by a frame known as a sash. Each frame and each sash can be constructed from horizontal and vertical members made of extruded aluminum or other structurally rigid materials. While aluminum is both strong and lightweight, it is thermally conductive and not energy efficient. To increase energy efficiency, frame and sash members can be constructed from pairs of aluminum extrusions that are thermally isolated from each other. Out of each pair, one extrusion faces an environment protected by the fenestration, for example, the interior environment, and the other extrusion faces an environment not protected by the fenestration, for example, the exterior environment. Thermal struts, structural foam, or other structural thermally isolating materials, can rigidly join the protected-environment-facing extrusion and corresponding unprotected-environment-facing extrusion. The thermal struts are made of thermally isolating material such as polyamide. The thermal struts are typically crimped into grooves in the extrusions by large crimping rollers. Alternatively, materials, such as polyurethane foam, can be poured or injected. The portion of the frame where the thermal strut or other structural thermally isolating material resides is referred to as a “thermal break.” The thermal break thermally isolates the protected-environment-facing extrusion from the unprotected-environment-facing extrusion. The glass panel is typically constructed of sealed double or triple panes of glass. The glass panes within the glass panel are thermally isolated from each other by air or gas between the panes.
One strategy to increase rain and wind performance is to pressurize the air space inside the frame. Weep holes, typically at the bottom and top of the frame, allow air pressure from wind to build up inside the frame. This air pressure becomes equalized with the outside pressure preventing wind driven rain from entering the frame. Many pressurized fenestration frames depend on interior glazing seals to hold the air pressure. Because the interior glazing seals reside in the protected environment, they are not exposed to harsh conditions. They are less likely to degrade over time compared with exterior glazing seals. The exterior glazing seals, on the other hand, can be exposed to ultra-violet light from the sun, as well as large temperature variations. Over time, they can lose its integrity and leak. Any rain that leaks into the window through the outside seal can drain through the weep holes.
Standards organizations, such as ASTM International, have developed standards to test rain leakage performance. One such standard is ASTM E331. This standard tests water penetration into exterior windows, skylights, doors, and curtain walls by applying a uniform and constant pressure difference between the interior and exterior of the fenestration. Some high-performance inswing terrace doors currently on the market can resist water penetration, as measured by ASTM E331, with a pressure difference of up to 718 Pascals (Pa) or 15 pounds per square foot (psf).